I present you with a Key : I have not heard of the like yet framed, since it pleased God to bring that mighty continent of America to light. Others of my countrymen have often, and excellently, and lately, written of the country, and none that I know beyond the goodness and worth of it.
This Key respects the native language of it, and happily may unlock some rarities concerning the natives themselves, not yet discovered.

Preface

The natives are very exact and punctual in the bounds of their lands, belonging to this or that prince or people, even to a river, brook, &c. And I have known them make bargain and sale amongst themselves for a small piece or quantity of ground ; notwithstanding a sinful opinion amongst many, that christians have right to heathen's land.

I was persuaded and am, that God's way is first to turn a soul from its idols, both of heart, worship, and conversation, before it is capable of worship to the true and living God... the two first principles and foundations of true religion, or worship of the true God in Christ, are repentance from dead works, and faith towards God, before the doctrine of baptism or washing, and the laying on of hands, which contain the ordinances and practices of worship; the want of which I conceive is the bane of millions of souls in England and all other nations professing to be Christian nations, who are brought by public authority to baptism and fellowship with God in ordinances of worship, before the saving work of repentance and a true turning to God.

Men's consciences ought in no sort to be violated, urged, or constrained. And whenever men have attempted any thing by this violent course, whether openly or by secret means, the issue has been pernicious, and the cause of great and wonderful innovations in the principallest and mightiest kingdoms and countries...

"Address to Parliament"

All civil states with their officers of justice in their respective constitutions and administrations are proved essentially civil, and therefore not judges, governors, or defenders of the spiritual or Christian state and worship.

It is the will and command of God that (since the coming of his Son the Lord Jesus) a permission of the most paganish, Jewish, Turkish, or antichristian consciences and worships, be granted to all men in all nations and countries; and they are only to be fought against with that sword which is only (in soul matters) able to conquer, to wit, the sword of God's Spirit, the Word of God.

God requireth not a uniformity of religion to be enacted and enforced in any civil state; which enforced uniformity (sooner or later) is the greatest occasion of civil war, ravishing of conscience, persecution of ChristJesus in his servants, and of the hypocrisy and destruction of millions of souls.

A civil sword (as woeful experience in all ages has proved) is so far from bringing or helping forward an opposite in religion to repentance that magistrates sin grievously against the work of God and blood of souls by such proceedings... Religion cannot be true which needs such instruments of violence to uphold it so.

The doctrine of persecution for cause of conscience, is most evidently and lamentably contrary to the doctrine of ChristJesus the Prince of Peace.

God needeth not the help of a material sword of steel to assist the sword of the Spirit in the affairs of conscience.

The God of Peace, the God of Truth will shortly seal this truth, and confirm this witness, and make it evident to the whole world, that the doctrine of persecution for cause of conscience, is most evidently and lamentably contrary to the doctrine of Christ Jesus the Prince of Peace.
Amen.

No man ever did, nor ever shall, truly go forth to convert the nations, nor to prophesy in the present state of witnesses against Antichrist, but by the gracious inspiration and instigation of the HolySpirit of God.

I have read … the last will and testament of the Lord Jesus over many times, and yet I cannot find by one tittle … that ever He would have put forth the least finger of temporal or civil power in the matters of His spiritual affairs...

No man ever did, nor ever shall, truly go forth to convert the nations, nor to prophesy in the present state of witnesses against Antichrist, but by the gracious inspiration and instigation of the Holy Spirit of God. … I know no other True Sender, but the most Holy Spirit.

'Tis true, those glorious first ministeriall gifts are ceased, and that's or should be the lamentation of all Saints... Yet I humbly conceive that without those gifts, it is no ground of imitation, and of going forth to Teach and Baptise the Nations, for, the Apostles themselves did not attempt that mighty enterprise, but waited at Jerusalem until the Holy Spirit descended on them, and inabled them for that mighty work.

The civil state of the nations, being merely and essentially civil, cannot (Christianly) be called "Christian states," after the pattern of that holy and typical land of Canaan, which I have proved at large in the Bloudy Tenent to be a nonesuch and an unparalleled figure of the spiritual state of the church of Christ Jesus, dispersed yet gathered to Him in all nations.The civil sword (therefore) cannot (rightfully) act either in restraining the souls of the people from worship, etc., or in constraining them to worship, considering that there is not a tittle in the New Testament of Christ Jesus that commits the forming or reforming of His spouse and church to the civil and worldly powers...

I observe the great and wonderful mistake, both our own and our fathers, as to the civil powers of this world, acting in spiritual matters. I have read … the last will and testament of the Lord Jesus over many times, and yet I cannot find by one tittle of that testament that if He had been pleased to have accepted of a temporal crown and government that ever He would have put forth the least finger of temporal or civil power in the matters of His spiritual affairs and Kingdom.
Hence must it lamentably be against the testimony of Christ Jesus for the civil state to impose upon the souls of the people a religion, a worship, a ministry, oaths (in religious and civil affairs), tithes, times, days, marryings, and buryings in holy ground...

The first grand design of Christ Jesus is to destroy and consume His mortal enemy antichrist. This must be done by the breath of His mouth in His prophets and witnesses. Now, the nations of the world have impiously stopped this heavenly breath and stifled the Lord Jesus in His servants. Now, it shall please the civil state to remove the state bars set up to resist the holy spirit of God in His servants (whom yet finally to resist is not in all the powers of the world), I humbly conceive that the civil state has made a fair progress in promoting the Gospel of Jesus Christ.

Opinions offensive are of two sorts: some savoring of impiety, and some of incivility.
Against the first, Christ Jesus never called for the sword of steel to help the sword of the spirit, that two-edged sword that comes out of the mouth of the Lord Jesus...
The second sort, to wit, opinions of incivility, doubtless the opinions as well as practices are the proper object of the civil sword...

Although the loose will be more loose (yet) possibly being at more liberty they may be put upon consideration and choice of ways of life and peace, yet, however, it is infinitely better that the profane and loose be unmasked than to be muffled up under the veil and hood of traditional hypocrisy, which turns and dulls the very edge of all conscience either toward God or man.

Such parents or children as aim at the gain and preferment of religion do often mistake gain and gold for godliness, godbelly for the true God, and some false for the true Lord Jesus.

The civil state is bound before God to take off that bond and yoke of soul oppression, and to proclaim free and impartial liberty to all the people of the three nations to choose and maintain what worship and ministry their souls and consciences are persuaded of; which act, as it will prove an act of mercy and righteousness to the enslaved nations, so is it of a binding force to engage the whole and every interest and conscience to preserve the common freedom and peace; however, an act most suiting with the piety and Christianity of the Holy Testament of Christ Jesus.

The civil state is humbly to be implored to provide in their high wisdom for the security of all the respective consciences, in their respective meetings, assemblings, worshipings, preachings, disputings, etc., and that civil peace and the beauty of civility and humanity be maintained among the chief opposers and dissenters.

There is no regularly constituted church of Christ on earth, nor any person qualified to administer any church ordinances; nor can there be until new apostles are sent by the Great Head of the Church for whose coming I am seeking.

There is no regularly constituted church of Christ on earth, nor any person qualified to administer any church ordinances; nor can there be until new apostles are sent by the Great Head of the Church for whose coming I am seeking.

A statement rejecting formal sectarian organizations and claims, this has been cited to a quotation in Picturesque America by William Cullen Bryant, p. 502, first published in 1872, but such a statement has not been located in the 1874 or 1894 editions.

Reply to disputation:

The reference for the above is: Picturesque America, or the Land We Live In, ed. William Cullen Bryant, New York: D. Appleton and Co., 1872, vol. 1, p. 502

In addition, Williams also said, “The apostasy… hath so far corrupted all, that there can be no recovery out of that apostasy until Christ shall send forth new apostles to plant churches anew.” (Underhill, Edward, “Struggles and Triumphs of Religious Liberty”, cited in William F. Anderson, “Apostasy or Succession, Which?”, pp. 238-39)

“We may conclude then that he left the church not because he had any doubts respecting the nature of baptism nor because he had been baptized by a layman but because he believed that no man is now authorized to administer the ordinances and that no true church can exist till the apostolic ministry shall be restored. With these views he could not conscientiously remain connected with any church nor regard his baptism as valid” Memoir of Roger Williams, the Founder of the State of Rhode-Island; James D. Knowles (Professor of Pastoral Duties in the Newton Theological Institution), Boston, Lincoln, Edmands and Co., 1834, p. 173 as read from Google Books on 2012/03/10

That Williams believed that apostasy had occurred and that a restoration by Christ of apostolic power / calling was required has many literary witnesses including baptist historians.

I do not believe these beliefs are under dispute within the scholarly community in any fashion.

"The most fascinating figure of America's formative seventeenth century," Roger Williams has now gained general acceptance as a symbol of a critical turning point in American thought and institutions. He was the first American to advocate and activate complete freedom of conscience, dissociation of church and state, and genuine political democracy. From his first few weeks in America he openly raised the banner of "rigid Separatism." In one year in Salem he converted the town into a stronghold of radical Separatism and threw the entire Bay Colony into an uproar. Banished for his views, after being declared guilty of "a frontal assault on the foundations of the Bay system," he escaped just as he was to be deported to England.
He settled in Providence with thirteen other householders and in one year formed the first genuine democracy, as well as the first church-divorced and conscience-free community in modern history. Williams felt that government is the natural way provided by God to cope with the corrupt nature of man. But since government could not be trusted to know which religion is true, he considered the best hope for true religion the protection of the freedom of all religion, along with non-religion, from the state.

Cyclone Covey in The Gentle Radical: Roger Williams (1966)

Williams' life and major works — the 1643 bestseller A Key Into the Language of America and the 1644 treatise The Bloudy Tenent of Persecution — inspire nothing less than awe. Williams showed up in Massachusetts in 1631 and immediately mixed it up with the theocrats there, staking controversial positions on hotly debated questions such as the presence of a disturbingly papal cross on the flag of England.
Two of his arguments would earn him exile: He insisted that the colonists had robbed the local Indians of their property (he called it "an unjust usurpation upon others' possessions") and, even worse, that civil magistrates had no business enforcing religious laws (lest "the wilderness of the world" engulf "the garden of the church").

The Bloudy Tenent of Persecution, released the same year as his friend John Milton's defense of the free press, Areopagitica, argued for "soul liberty" for all people, "paganish, Jewish, Turkish, or anti-christian." Such ideas were far ahead of their time — perhaps even our time... Williams' ideas infused the charters of New Jersey, Pennsylvania, and other colonies with protections for religious freedom. And his notions of a fully secular state found their way into the writings of John Locke, who would have a seminal influence on Jefferson, Madison, and other Founders. One wishes that America had taken even more from Williams and what Gaustad calls his "bequest...of liberty, responsibility, and civility."

The English... justified their grabbing of Indian land by claiming that these simple folk did not really believe in property rights. On the contrary, Williams observed, "the Natives are very exact and punctual in the bounds of their Lands, belonging to this or that Prince or People," even bargaining among themselves for a small piece of ground.